1. Field of the Invention
This invention relates to a cross member being extended in the width direction of an automobile body and provided in the intermediate portion of an automobile body floor in the longitudinal direction thereof. The cross member crosses a floor tunnel in the automobile body floor.
The present application is based on Japanese Patent Applications No. Hei. 10-37217 and No. Hei. 10-327022, which are incorporated herein by reference.
2. Description of the Related Art
There is a recent tendency to take the deformation of the passenger room not only by the head-on collision load but also by the side impact load seriously.
On the other hand, the time is ripe for putting to practical use an automobile body structure made of aluminum-alloy in order to meet a demand for decreasing automobile body weight.
However, it is not easy to apply spot welding to the aluminum alloy, so if the conventional method of welding the steel sheets is used for welding of aluminum alloy, it is unavoidable that the production cost rises sharply.
Further, at the central portion of an automobile body floor in the width direction thereof, there is provided a so-called floor tunnel having a recessed surface opening downward and being continuous in the longitudinal direction of the automobile floor, in which a propeller shaft and an exhaust pipe are provided. And a cross member crossing the floor tunnel is extendedly provided in the lateral direction of the floor. Since the floor tunnel is opened downward, the closed section of the cross member crossing the floor tunnel has to be divided into parts in the intersecting portion.
In view of securing bending strength as much as possible, it is not preferable to divide into parts the cross member which is to play an important part as a reinforcing member against side impact because dividing the cross member into parts causes the strength to decrease.
In order to secure the rigidity of the intersecting portion where the cross member and the floor tunnel intersect, a reinforcing member may be added to the cross member. However, the addition of such a reinforcing member thereto incurs the complication of the process of producing the intersecting portion, which leads to an increase in production cost.